The present invention relates to an automotive brake rotor and a wheel bearing assembly.
Various kinds of wheel bearing assemblies are known including ones for driving wheels and ones for non-driving wheels. FIG. 27 shows a wheel bearing assembly for a driving wheel. It comprises an outer member 3 having two raceways 3a, 3b formed on its inner peripheral surface, an inner member 1 having two raceways 1a, 1b opposite the respective raceways 3a, 3b, and rolling elements or balls 8 disposed between the raceways 3a, 3b on the outer member 3 and the raceways 1a, 1b on the inner member 1 in two rows. The inner member 1 has a flange 2 adapted to be secured to a wheel and is formed with a splined bore 9 into which is inserted a drive shaft.
A brake rotor 5 is positioned by bolts 18 to the outer side 2a of the flange 2 and secured between the outer side 2a and the wheel hub by bolts 7. Any runout of the brake rotor 5 can cause vibrations or squeal during braking, or uneven wear of the brake rotor and/or brake pad.
Brake rotors and wheel bearings are usually delivered to a car manufacturer, who assemble them together. It has been an ordinary practice to adjust to minimize runout of the brake rotor 5 when or after assembling the rotor and the wheel bearing, by e.g. adjusting the angular position of the mounting bolts 7. But such work is troublesome and inefficient.
An object of the invention is to provide a brake rotor and a wheel bearing assembly that are reliable and need no runout adjustment at a car manufacturer.
According to the invention, a brake rotor is provided which is mounted to a rotary member of a wheel bearing assembly for rotatably supporting a wheel on a vehicle body by means of double-row rolling elements. The maximum runout variation of a mounting surface on the side of the brake rotor abutting the rotary member is restricted within a predetermined value.
By restricting the maximum runout variation of the mounting surface on the side of the brake rotor abutting the rotary member within a predetermined value, runout of the brake rotor mounted to the rotary member is suppressed low within a desired range and troublesome runout adjustment after assembling has become unnecessary.
By restricting the maximum runout variation of a back side of the mounting surface to which a wheel hub is mounted within a predetermined value, it is possible to suppress the runout of the brake rotor.
By restricting it to 50 xcexcm or less, the brake rotor will be reliable and will not require any runout adjustment after assembly.
By restricting the runout variation per cycle of the mounting surface or its back side within a predetermined value, it is possible to smoothen the runout of the brake rotor.
According to the invention, the runout variation per cycle of the mounting surface should be restricted to 30 xcexcm or less.
According to the invention, the maximum difference between the peak values of crests or the maximum difference between the peak values of troughs in each runout cycle of the mounting surface or its back side should be restricted within a predetermined value. Thereby it is possible to suppress the runout of the brake rotor to a lower value. The predetermined value should be not more than 30 xcexcm.
According to the invention, it is preferable that the frequency per rotation of runout of the mounting surface be a multiple of the number of wheel mounting bolts or the number of the mounting bolts be a multiple of the frequency. Thereby it is possible to make uniform the deformation of the brake rotor due to tightening force applied to the mounting bolt and suppress the runout of the brake rotor resulting from the deformation of the brake rotor.
According to the invention, there is provided a wheel bearing assembly comprising an outer member having two raceways on its inner surface, an inner member having two raceways on its outer surface, opposite to the respective raceways on the outer member, and two rows of rolling elements mounted between the opposed raceways, wherein a wheel mounting flange is formed on one of the outer member and the inner member, wherein one side of the wheel mounting flange is a mounting surface for a brake rotor, characterized in that the maximum runout variation of the brake rotor mounting surface is restricted within a predetermined value.
By restricting the maximum variation of runout of the brake rotor mounting surface of the wheel mounting flange within a predetermined value, it is possible to suppress runout of the brake rotor without carrying out troublesome runout adjustment after assembling.
According to the invention, the predetermined value should be 50 xcexcm and preferably 30 xcexcm.
By restricting the runout variation per cycle of the brake rotor mounting surface within a predetermined value, it is possible to smoothen the runout of the braking surface of the brake rotor.
By restricting the maximum difference between the peak values of crests or the maximum difference between the peak values of troughs in each cycle of runout of the brake rotor mounting surface within a predetermined value, it is possible to suppress the runout of the braking surface of the brake rotor.
It is preferable that the frequency per rotation of runout of the brake rotor mounting surface be a multiple of the number of wheel mounting bolts or the number of the wheel mounting bolts be a multiple of the frequency. Thereby it is possible to make uniform the deformation of the brake rotor due to tightening force applied to the mounting bolt and suppress the runout of the brake rotor resulting from the deformation of the brake rotor.
Also, in the arrangement in which the brake rotor mounting surface is the outer side of the wheel mounting flange, by inclining this side outwardly toward the tip of the wheel mounting flange, when the brake rotor and the wheel hub are superposed and tightened by wheel mounting bolts, the wheel mounting flange is resiliently deformed, so that the outer peripheral portion of the brake rotor mounting surface is pressed hard against the brake rotor. Thus, the brake rotor is stably supported by the outer peripheral portion. In this case too, by also restricting the maximum runout variation of the brake rotor mounting surface within a predetermined value, it is possible to suppress runout of the braking surface during rotation of the brake rotor.
The inclination angle of the brake rotor mounting surface is preferably 20xe2x80x2 or less. If this angle is greater than needed, even if the wheel mounting flange is resiliently deformed, the inner peripheral portion of the brake rotor may become out of contact with the brake rotor mounting surface, so that the mounting of the brake rotor becomes unstable. The upper limit of the inclination angle that will not become unstable is determined at 20xe2x80x2.
By setting the degree of flatness and circumferential flatness of the outer peripheral portion of the brake rotor mounting surface at 30 xcexcm or less, it is possible to suppress runout of the braking surface during rotation of the brake rotor pressed hard against the outer peripheral portion.
As shown in FIG. 25A, the circumferential flatness is measured as described below. The wheel mounting flange 2 is rotated with the probe of a measuring device such as a dial gauge 22 in contact with the outer peripheral portion of the side 2a, which is the brake rotor mounting surface of the wheel mounting flange 2. FIG. 25B is a graph showing undulation picked up by the probe of the dial gauge. The circumferential flatness is the minimum distance 6 between two parallel lines L1 and L2 between which the undulation is contained.
The wheel mounting flange may be formed integrally with the outer member or the inner member.
By mounting the above-mentioned brake rotor with less runout on the brake rotor mounting surface, the runout of the braking surface of the brake rotor during rotation can be suppressed.
According to the present invention, there is also provided a wheel bearing assembly comprising an outer member having two raceways on its inner surface, an inner member having two raceways on its outer surface so as to be opposite to the two raceways on the outer member, and two rows of rolling elements mounted between the opposed raceways, a wheel mounting flange being formed on the inner member, characterised in that a brake rotor is integrally formed on the wheel mounting flange.
By forming a brake rotor integrally with the wheel mounting flange, the mounting of the brake rotor and runout adjustment after assembly can be eliminated.
By restricting the maximum runout of the braking surface of the brake rotor below a predetermined value, the runout of the braking surface of the brake rotor during rotation can be suppressed without need of troublesome runout adjustment by the customer.
The predetermined value should be 100 xcexcm or preferably 50 xcexcm.
If the wheel mounting flange is mounted on the inner member, a drive shaft may be mounted in the inner member, or the inner member may be formed integrally with an outer coupling of a constant-velocity joint.
The inner member may comprise a first inner member having an outboard raceway and a second inner member having an inboard raceway, and the second inner member may be an outer coupling or spindle of a constant-velocity joint.
By inseparably coupling the first and second inner members together by deformation, no nuts are needed and a smaller number of parts, smaller weight and smaller axial length of the assembly are achieved.
By forming a dimension-controlled negative axial clearance between the rolling elements and the raceways, it is possible to provide a wheel bearing assembly high in rigidity, and in a state assembled in a vehicle body, while the vehicle is turned, it is possible to prevent the member on the side having the wheel mounting flange from inclining toward the member on the fixed side to eliminate uneven contact between the brake rotor mounted to the wheel mounting flange and the brake pads, thus preventing uneven wear of both of them. Thus, coupled with the effect by restricting the maximum variation of runout of the brake rotor mounting surface within a predetermined value, it is possible to suppress runout of the braking surface during rotation of the brake rotor.
At least one of the two raceways on the inner member may be formed on a separate raceway member fixed to the inner member. This facilitates control of the axial clearance between the rolling elements and the raceways.
By inseparably coupling the inner member and the separate raceway member together by plastic deformation, no nuts are needed and a smaller number of parts, smaller weight and smaller axial length of the assembly are achieved.
According to this invention, there is provided a wheel bearing assembly wherein one of the outer member and the inner member that carries the wheel mounting flange is rotatable and the other is nonrotatable and wherein the outer member and inner member defines an annular space therebetween in which are disposed rolling elements. The wheel bearing assembly further comprises a slinger fixed to the one of the outer and inner members, seal members for sealing both sides of the annular space, an encoder having multiple magnetic poles and fixed to the slinger, a sensor for sensing fluctuations in the magnetic flux produced by the encoder when the encoder rotates and for producing a signal indicative of the revolving speed of the encoder, and a rotational speed detector for receiving the signal and for calculating the revolving speed of the one member based on the signal.
In comparison with the arrangement in which a rotational speed detector is separately provided, a compact and light-weight assembly is provided with a greater freedom of design.
According to this invention, there is also provided a wheel bearing assembly wherein the wheel mounting flange is fastened to a brake rotor by bolts inserted through bolt holes formed in the flange, the wheel bearing assembly further comprising arrangements for preventing the bolts from turning in the respective bolt holes.
This reduces the surface pressure between serrations formed at the neck of the bolt and the inner wall of the bolt hole and thus prevents strains from producing on the side of the flange on which the brake rotor is mounted.
The arrangement for preventing the bolts from turning may comprise a bolt head having a noncircular cross-section, and a protrusion formed on the wheel mounting flange near each of the bolt holes and engaging the head to prevent the each bolt from turning in the bolt hole.
The noncircular head may have a flat side face formed thereon, or have a knurled surface, or an oval cross-section.
The protrusions may be pressed against the respective heads by plastic deformation.